This section provides background information relating to the present disclosure, which is not necessarily prior art.
In traditional intra-base station carrier aggregation, a PUCCH (Physical Uplink Control Channel) may be transmitted only via an uplink primary carrier, a PUSCH (physical Uplink Shared Channel) and a SRS (Sounding Reference Signal) may be transmitted via a SCC (Secondary Component Carrier), and a PRACH (Physical Random Access Channel) may be transmitted only when a terminal is to access a certain carrier.
The following three basic types of carrier aggregation are supported by any version after LTE (Long Term Evolution) Rel-12: 1) the FDD (Frequency Division Duplexing) carrier aggregation, or the TDD (Time Division Duplexing) carrier aggregation having the same intra-band configuration; 2) the TDD carrier aggregation having different uplink and downlink configurations; and 3) the carrier aggregation between FDD and TDD.
In particular, in a case that a larger number of small base stations are deployed and there exists a direct connection of optical fiber between a small base station and a macro base station, the traditional method where a PUCCH may be transmitted only via a primary carrier will causes the following issues for all of the three scenarios above: 1) it cannot share the burden of PUCCH for a node of a macro base station to release the burden of uplink control channel of the macro cell, especially in a case that the uplink time slots of the primary carrier is less and the HARQ (Hybrid Automatic Repeat Request) RTT (Round-Trip Time) of the primary carrier and a secondary carrier are different (for example, in a case that FDD cooperates with TDD while a TDD carrier serving as a primary carrier, or in a case of TDD having different configurations; it should be noted that the number of unlink subframes should be at most 60% of the total number of subframes); 2) the power consumption of the uplink transmission is over high when a macro cell carrier servers as a primary carrier; and 3) in a case that a TDD carrier servers as a primary carrier and the number of uplink subframes is less, it tends to have a higher PUCCH feedback time-delay and a higher retransmission time-delay of downlink data, effecting the QoS (Quality of Service) feeling of a user.